package com.chinatechstar.component.commons.utils;

import java.io.UnsupportedEncodingException;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;

public class MD5Util {

    private static final String HEX_NUMS_STR="0123456789ABCDEFSTEPLEI";
    private static final Integer SALT_LENGTH = 12;   
       
    /**   
     * 将16进制字符串转换成字节数组   
     * @param hex   
     * @return   
     */  
    public static byte[] hexStringToByte(String hex) {   
        int len = (hex.length() / 2);   
        byte[] result = new byte[len];   
        char[] hexChars = hex.toCharArray();   
        for (int i = 0; i < len; i++) {   
            int pos = i * 2;   
            result[i] = (byte) (HEX_NUMS_STR.indexOf(hexChars[pos]) << 4    
                            | HEX_NUMS_STR.indexOf(hexChars[pos + 1]));   
        }   
        return result;   
    }   
  
       
    /**  
     * 将指定byte数组转换成16进制字符串  
     * @param b  
     * @return  
     */  
    public static String byteToHexString(byte[] b) {   
        StringBuffer hexString = new StringBuffer();   
        for (int i = 0; i < b.length; i++) {   
            String hex = Integer.toHexString(b[i] & 0xFF);   
            if (hex.length() == 1) {   
                hex = '0' + hex;   
            }   
            hexString.append(hex.toUpperCase());   
        }   
        return hexString.toString();   
    }   
       
    /**  
     * 验证口令是否合法  
     * @param password  
     * @param passwordInDb  
     * @return  
     * @throws NoSuchAlgorithmException  
     * @throws UnsupportedEncodingException  
     */  
    public static boolean validPassword(String password, String passwordInDb)   
            throws NoSuchAlgorithmException, UnsupportedEncodingException {   
        //将16进制字符串格式口令转换成字节数组   
        byte[] pwdInDb = hexStringToByte(passwordInDb);   
        //声明盐变量   
        byte[] salt = new byte[SALT_LENGTH];   
        //将盐从数据库中保存的口令字节数组中提取出来   
        System.arraycopy(pwdInDb, 0, salt, 0, SALT_LENGTH);   
        //创建消息摘要对象   
        MessageDigest md = MessageDigest.getInstance("MD5");   
        //将盐数据传入消息摘要对象   
        md.update(salt);   
        //将口令的数据传给消息摘要对象   
        md.update(password.getBytes(StandardCharsets.UTF_8));
        //生成输入口令的消息摘要   
        byte[] digest = md.digest();   
        //声明一个保存数据库中口令消息摘要的变量   
        byte[] digestInDb = new byte[pwdInDb.length - SALT_LENGTH];   
        //取得数据库中口令的消息摘要   
        System.arraycopy(pwdInDb, SALT_LENGTH, digestInDb, 0, digestInDb.length);   
        //比较根据输入口令生成的消息摘要和数据库中消息摘要是否相同   
        //口令正确返回口令匹配消息
        //口令不正确返回口令不匹配消息
        return Arrays.equals(digest, digestInDb);
    }   
  
  
    /**  
     * 获得加密后的16进制形式口令  
     * @param password  
     * @return  
     * @throws NoSuchAlgorithmException  
     * @throws UnsupportedEncodingException  
     */  
    public static String getEncryptedPwd(String password) {
        //声明加密后的口令数组变量   
        byte[] pwd = null;   
        //随机数生成器   
        SecureRandom random = new SecureRandom();   
        //声明盐数组变量   
        byte[] salt = new byte[SALT_LENGTH];   
        //将随机数放入盐变量中   
        random.nextBytes(salt);   
  
        //声明消息摘要对象   
        MessageDigest md = null;   
        //创建消息摘要   
        try {
            md = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException();
        }
        //将盐数据传入消息摘要对象   
        md.update(salt);   
        //将口令的数据传给消息摘要对象   
        md.update(password.getBytes(StandardCharsets.UTF_8));
        //获得消息摘要的字节数组   
        byte[] digest = md.digest();   
  
        //因为要在口令的字节数组中存放盐，所以加上盐的字节长度   
        pwd = new byte[digest.length + SALT_LENGTH];   
        //将盐的字节拷贝到生成的加密口令字节数组的前12个字节，以便在验证口令时取出盐   
        System.arraycopy(salt, 0, pwd, 0, SALT_LENGTH);   
        //将消息摘要拷贝到加密口令字节数组从第13个字节开始的字节   
        System.arraycopy(digest, 0, pwd, SALT_LENGTH, digest.length);   
        //将字节数组格式加密后的口令转化为16进制字符串格式的口令   
        return byteToHexString(pwd);   
    }   

    
    /*** 
     * MD5加码 生成32位md5码 
     */  
    public static String string2MD5(String inStr){  
        MessageDigest md5 = null;  
        try{  
            md5 = MessageDigest.getInstance("MD5");  
        }catch (Exception e){  
            System.out.println(e);
            e.printStackTrace();  
            return "";  
        }  
        char[] charArray = inStr.toCharArray();  
        byte[] byteArray = new byte[charArray.length];  
  
        for (int i = 0; i < charArray.length; i++)  
            byteArray[i] = (byte) charArray[i];  
        byte[] md5Bytes = md5.digest(byteArray);  
        StringBuffer hexValue = new StringBuffer();  
        for (int i = 0; i < md5Bytes.length; i++){  
            int val = (md5Bytes[i]) & 0xff;  
            if (val < 16)  
                hexValue.append("0");  
            hexValue.append(Integer.toHexString(val));  
        }  
        return hexValue.toString();  
  
    }  
  
    /** 
     * 加密解密算法 执行一次加密，两次解密 
     */   
    public static String convertMD5(String inStr){  
  
        char[] a = inStr.toCharArray();  
        for (int i = 0; i < a.length; i++){  
            a[i] = (char) (a[i] ^ 't');  
        }  
        String s = new String(a);  
        return s;  
  
    }  
  
    // 测试主函数  
    public static void main(String[] args) {
        String s = "123456";
        System.out.println("原始：" + s);  
        System.out.println("MD5后：" + string2MD5(s));  
        System.out.println("加密的：" + convertMD5(s));  
        System.out.println("解密的：" + convertMD5(convertMD5(s)));  
  
    }  

}
